The operator in question is guaranteed to produce a tagged value that is
not equal to the-hole, it however does not guarantee the value to be a
HeapObject. The correct representation hence is {kTagged}.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-665587
BUG=chromium:665587

Review-Url: https://codereview.chromium.org/2504183002
Cr-Commit-Position: refs/heads/master@{#41032}